National Geographic has a piece on the threat to the world’s electric grids from potential solar storms as the Sun reaches its solar maximum in 2013.

The biggest impacts come from coronal mass ejections (CMEs), cloud-like bundles of plasma that race off the Sun’s upper atmosphere, or corona, at millions of miles per hour during periods of intense surface activity. Luckily not every CME is a threat to Earth as they are highly directional and can miss Earth entirely or strike only glancing blows.

A direct hit, carrying currents of trillions of charged particles, could knock out communications, scramble GPS, and leave thousands or even millions without power for days to months. The ubiquitous electrical grid on Earth’s surface acts like an antenna, allowing these currents to flow into transmission lines and can overload the distribution system. Serious problems arise because the extra currents from solar storms are direct current (DC) flows, and the electricity transmission system is used to handling alternating current (AC) flows.

Under the right conditions, solar storms can create extra electrical currents in Earth’s magnetosphere—the region around the planet controlled by our magnetic field. The electrical power grid is particularly vulnerable to these extra currents, which can infiltrate high-voltage transmission lines, causing transformers to overheat and possibly burn out.

“The concern is if the electric grid lost a number of transformers during a single storm, replacing them would be difficult and time-consuming,” said Rich Lordan, senior technical executive for power delivery and utilization at the Electric Power Research Institute (EPRI).

“These power transformers are very big devices, and the lead time to get a replacement can be two months—if there’s a spare one stored nearby. If a utility has to order a new one from the manufacturer, it could take six months to up to two years to deliver.”

In 1989 the transmission system for Canada’s Hydro Quebec electricity provider collapsed during a solar storm, leaving millions of people without power for nine hours or more. And the “Halloween storms” of 2003 triggered blackouts in the city of Malmö, Sweden, and likely caused transformer failures in South Africa.

The largest solar storm ever recorded was in 1859 when communications infrastructure was limited to telegraphs. The giant solar storm hit telegraph offices around the world and caused a giant aurora visible as far south as the Caribbean Islands. Some telegraph operators reported electric shocks. Papers caught fire. And many telegraph systems continued to send and receive signals even after operators disconnected batteries. A storm of similar magnitude today could cause up to $2 trillion in damage globally, according to a 2008 report by the National Research Council. Read more about the “Carrington Event” here.

If the storm is expected to be severe enough and given two or three days lead time, Earth can escape disaster by shutting down the grid in those regions most likely to be affected (the areas closest to the poles). This, of course, would lead to blackouts in those regions. Both the US and Europe are putting in place early warning systems to enable grid operators to make the appropriate changes to their grids.

“It’s important to be as well-educated about the Sun as possible,” he said. “There’s a recognition in the emergency management community and other levels of government that, as best we can, we need to communicate about space weather.

“If something does happen, even if we didn’t predict it very well, the idea is that we can get the word out quickly, and people will know what to do.”

The following video shows the massive coronal mass ejection on June 7, 2011.

UPDATE: On August 6th Reuters reported that U.S. government scientists have cautioned users of satellite, telecommunications and electric equipment to prepare for possible disruptions over the next few days following the eruption of three large solar flares from the Sun. The solar storms could affect communications and global positioning system (GPS) satellites and might even produce an aurora visible as far south as Minnesota and Wisconsin.